This invention is related to a method of synthesizing organometallic materials. More specifically, this invention is directed to a method for synthesizing ruthenium and osmium compounds.
Ruthenium (Ru), osmium (Os), and their oxides are materials under consideration for use as electrodes in future semiconductor devices (e.g. ferroelectric memory and logic chips). These materials possess attractive physical properties, such as low electrical resistance, high work functions, inter-layer chemical diffusion resistance, and thermal and oxidative stability. In addition, Ru, Os and their oxides produce thin films with lattice parameters and thermal expansion coefficients that make them compatible with many dielectric materials under consideration for future semiconductor devices.
Chemical vapor deposition (CVD) is a technique that is widely utilized in the fabrication of semiconductor devices to produce the layers of materials that make the devices. CVD chemical compounds (referred to as precursors) are transported in the vapor phase to or near a surface where they decompose by some means (e.g. thermal, chemical or plasma activation) to produce a solid film of a desired material composition. The use of CVD techniques to produce both ruthenium and ruthenium oxide thin films for semiconductor devices has been demonstrated in a number of publications. See, for example, WO 00/12766. Ruthenium and osmium compounds suitable for use as CVD precursors will be required if these materials are incorporated into commercial semiconductor devices using the CVD technique. Further, there have been promising reports of employing both cyclopentadienyl ruthenium (II) complexes and ruthenium (0) carbonyl complexes as CVD precursors. U.S. Pat. No. 6,114,557 discloses a synthetic route to the ruthenium (0) carbonyl complexes.
The preparation of compounds with the formula LxM(CO)Y [L=a neutral ligand, M=Ru or Os, x=1 to 4, and y=1 to 5] dates back to the late 1960""s when their preparation was first described in the scientific literature. The general preparative route to these compounds involves the reaction of Ru3(CO)12 with a ligand, in the presence of a solvent at reflux. The solvent of choice for these reactions was generally benzene. Reactions of Ru3(CO)12 with dienes, thiols and phosphines occurred in the solvent benzene at reflux. See, Johnson et al., Nature, 1967, pp. 902-3. Preparation of (diene)Ru(CO)3 complexes including C6H8Ru(CO)3 and C8H12Ru(CO)3 complexes were prepared from the reaction of Ru3(CO)12 with 1,3-cyclohexadiene and 1,5-cyclooctadiene respectively, in refluxing benzene. See, Cowles, et al., Chem. Comm, 1969, p. 392.
A second route to [(diene)Ru(CO)3] compounds involves displacement reactions using C8H12Ru(CO)3 as the starting material. As described above, this compound is prepared by refluxing in benzene a mixture of 1,5-cyclooctadiene and Ru3(CO)12. The C8H12Ru(CO)3 is then reacted with another diene (for example C6H8) also in refluxing benzene, to produce the desired product. See, Burt et al., J.C.S. Dalton, 1975, pp. 731-6. Further, alkene ligands displaces C8H12 to form (alkene)Ru(CO)3 complexes, with high yields. See, Domingos, et al., J.C.S. Dalton, 1975, pp. 2288-91.
Finally, U.S. Pat. No. 6,114,557 discloses an improved route to compounds with the formula LxM(CO)Y [L=a neutral ligand, M=Ru or Os, x=1 to 4, and y=1 to 5]. The reaction route they utilize is nearly identical to that described above, except that the solvent system is slightly modified. Thus, Ru3(CO)12 is reacted with a ligand, in a solvent other than benzene. Specifically higher boiling solvents (for example toluene) are employed. The ""557 patent discloses that a higher boiling solvent system leads to an increased reaction rate and increased product yield.
Although there is a great deal of prior art in the scientific chemical literature disclosing information about compounds of the type LxM(CO)Y [L=a neutral ligand, M=Ru or Os, x=1 to 4, and y=1 to 5], it is believed that the synthetic schemes discussed above describes their synthesis.
While prior art solutions employ a non-reactive solvent system for the synthesis of compounds of the type LxM(CO)Y [L=a neutral ligand, M=Ru or Os, x=1 to 4, and y=1 to 5], there has been no teaching or suggestion for a neat, or solvent-free, reaction route. In addition, the prior art references show that the synthesis of carbonyl-based complexes, i.e., ruthenium complexes, to require a long reaction time. For example, in U.S. Pat. No. 6,114,557, a reaction which produces (C6H8)Ru(CO)3 is reported to take place over a 24 hour time period. Therefore, it is desirous to have a novel neat synthesis approach (where the ligand, L, acts as both the solvent and as a reactant) that is not taught or suggested by the prior art. The neat reaction route enables the reaction to be accomplished more quickly than by using prior art methods, while still producing the desired product in high yield. Using a neat reaction system is also preferable because it simplifies the synthetic process, since fewer components are needed.
This invention is directed to a method for synthesizing a carbonyl-substituted compound under neat conditions comprising refluxing a metal carbonyl compound with an excess of neutral ligand to produce a first mixture; evaporating any excess neutral ligand from the first mixture to produce a second mixture; and distilling the second mixture to produce the carbonyl based compound. The metal carbonyl is a ruthenium or osmium carbonyl complex. The neutral ligand may be phosphines, phosphites, amines, arsines, stibenes, ethers, sulfides, alkylidenes, nitrites, isonitriles, thiocarbonyls, linear, branched, or cyclic monoalkenes, linear, branched, or cyclic dienes, linear, branched, or cyclic trienes, bicyclic alkenes, bicyclic dienes, bicyclic trienes, tricyclic alkenes, tricyclic dienes, tricyclic trienes, and alkynes.
This invention is also directed to a method for synthesizing a carbonyl-based compound having the formula LxM(CO)y, wherein L=a neutral ligand, x=1-4, M=Ru or Os and y=1-5, under neat conditions comprising refluxing a metal carbonyl compound with the formula Mn(CO)z, where M=Ru or Os, n=3, z=12, with an excess of neutral ligand to produce a first mixture; evaporating any excess neutral ligand from the first mixture to produce a second mixture; and distillation of the second mixture to produce the carbonyl based compound. The carbonyl is based on the formula LxM(CO)y, wherein L is a neutral ligand, x=1, M=Ru or Os and y=3.
This invention is also directed to synthesizing a carbonyl-based compound under neat conditions comprising refluxing a metal carbonyl compound with an excess of neutral ligand to produce a first mixture and distilling any excess neutral ligand from the first mixture to produce a second mixture; and distilling the second mixture to produce the carbonyl-based compound.
Furthermore, this invention provides a method for synthesizing a ruthenium complex under neat conditions refluxing a metal carbonyl compound with the formula Mn(CO)z, where M=Ru, n=3, z=12, with an excess of neutral ligand to produce a first mixture; evaporating any excess neutral ligand from the first mixture to produce a second mixture; and distilling the second mixture to produce the carbonyl-based compound. Here, the ruthenium based complex comprises the formula LxM(CO)y, wherein L=C6H8, x=1, M=Ru and y=3.
This invention is also directed to a method for synthesizing an osmium complex under neat conditions to reflux a metal carbonyl compound with the formula Mn(CO)z, where M=Os, n=3, z=12, with an excess of neutral ligand to produce a first mixture; vaporating any excess neutral ligand from the first mixture to produce a second mixture; distilling the second mixture to produce the carbonyl based compound. The carbonyl based compound can be described by the formula LxM(CO)y, wherein L=C6H8, x=1, M=Os and y=3.
As used herein, the method for synthesis takes the steps of several steps. The word reacting is used, but this term, for purposes of this invention, is interchangable with related terms such as mixing, combining, stirring, refluxing, heating, etc. No reaction necessarily takes place, but a chemical reaction is not precluded. The removing steps can be described as evaporating, distilling, precipitating, filtering, separating, etc.
The present invention potentially reduces the volume of material the reaction apparatus must hold to produce similar amounts of product, minimizing the size of the reaction apparatus. Using a similar argument, the absence of solvent also reduces the energy that must be added to the system to bring the mixture to reflux. In addition, after the reaction has been completed, the excess ligand can be more easily recovered/recycled for reuse in this process because it can be distilled directly from the reaction products in high purity, and with a high recovery yield.
To produce compounds of the general type LxM(CO)y [L=a neutral ligand, M=Ru or Os, x=1-4, and y=1-5], Ma(CO)b [where M=Ru or Os], a=1-3, b=5-12, is reacted directly with L under neat conditions (in the absence of a solvent system). Most preferably, the reaction is accelerated by providing a large excess of the ligand L, heating the reaction mixture (ideally to reflux, although other temperatures are allowed and may be desired), and agitating the reaction mixture.